The present limited identification of the products of the reaction with DNA of the ultimate carcinogenic diolepoxide metabolite of benzo(a)pyrene will be extended to cover all DNA products, and also those from other hydrocarbons. Evidence whether attack of the carcinogen on the cellular genome is random or specific will be obtained using various methods for DNA and chromatin fractionation. The quantitative relationship between carcinogen-DNA reaction and the induction of ouabain or 8-azaquanine resistance in mammalian cells in culture, along with biochemical studies of the residual HGPRTase enzyme present in the appropriate mutants will allow the molecular mechanism for the induction of mutations by hydrocarbons to be assessed. In vitro cell transformation of hamster and human cells by diolepoxide metabolites of hydrocarbons will be related to the mutagenic action of these compounds at 2 genetic loci. Particular attention will be given to the transformation of human cells. Fibroblast cultures from individuals showing the syndromes of the cancer-prone diseases of Xeroderma pigmentosum, Ataxia telengectasia, and hereditary retinoblastoma have been obtained and will be used in transformation studies, with the expectation that these cells will respond more readily to DNA damaging agents. A new technique, involving the growth of human cells on Sephadex microbeads in suspension culture, will attempt to overcome the practical problems introduced by the low frequency (one in 10 to the 7th power treated cells) of human cell transformation.